- In May 2021, Japanese scientists made a big scientific discovery when they identified an ultra-high-energy cosmic ray dubbed ‘Amaterasu’ after the Japanese sun goddess.
Discovery of Amaterasu
- Dr. Toshihiro Fujii, an astronomer from Osaka Metropolitan University, found the Amaterasu cosmic ray.
- Amaterasu has an exceptionally high energy level of 240 exa-electron-volt (EeV).
- When compared to man-made accelerators, this energy is approximately 40 million times greater than that of protons accelerated by the Large Hadron Collider (LHC).
The Mysterious Origin of Amaterasu
- Amaterasu seemed to have sprung from an empty region of the universe.
- Theories advanced by Dr Fujii include an undiscovered source, interaction with a strong magnetic field, and the need for new physics models.
- Previous Records: The “Oh My God” particle, discovered in 1991 with an energy of 320 EeV, is still the most energetic cosmic ray ever discovered.
The Nature and Impact of Cosmic Rays
- Cosmic rays are streams of energetic particles, including protons and alpha particles, that originate in space and from the sun.
- Interaction with Earth: The majority of cosmic rays lose energy in the Earth’s atmosphere, preventing hazardous high-intensity rays from reaching the surface.
- Historical Importance: Since the 1930s, studies of cosmic rays have led to the discovery of numerous subatomic particles, albeit their sources and high energy remain unknown.
Cosmic Ray Types and Origins
- GCR (Galactic Cosmic Rays): Coming from outside our solar system, maybe from supernovae.
- Cosmic Rays of the Sun: Emitted by the sun, particularly in solar flares, and predominantly composed of protons.
- Composition Analysis: Studies demonstrate that the helium-to-hydrogen nuclei mass ratio in cosmic rays is similar to the composition of the early cosmos.
The Effects of High-Energy Cosmic Rays
- UHECRs (ultra-high-energy cosmic rays): Extragalactic particles having energy greater than 1 EeV.
- Space Travel Limitations: UHECRs with more than 60 EeV energy experience suppression owing to contact with cosmic microwave background (CMB) radiation, limiting their travel distance to 50-100 megaparsecs.
Source: https://www.thehindu.com/sci-tech/science/amaterasu-cosmic-ray-physics-explained/article67690711.ece#:~:text=The%20Amaterasu%20cosmic%20ray%20had%20an%20energy%20of%20240%20EeV,%2Dsmasher%2C%20located%20in%20Europe.